should I have my 15yr. old daughter, my 11yr. and my 5yr. old sons undergo a Psycho-educational evaluation?

I have a 15yr. old daughter, who was diagnosed with Auditory Deficiency Disorder at the end of 4Th grade. After her diagnosis nothing really has happened, unless you count the IEP meetings, we have every year, where truly I don't see the benefit. She has been struggling with school all her life, however, and regardless of our efforts she just can't seem to get at least B's and C's in school. I try as much as I can to encourage her every quarter to try a little harder without any success. I have an, 11yr.old son diagnosed with ADHD and just recently my youngest son has undergone intensive evaluations for learning disabilities(or even Autism). The therapist recommended that I take my 5yr. old for a Psycho-educational evaluation. My question is: given our history, should I conduct the same evaluation on my three children, most importantly on my 15yr. old daughter? please advise.